Um die anderen Arten von Veröffentlichungen zu diesem Thema anzuzeigen, folgen Sie diesem Link: Exfoliace.
Dissertationen zum Thema „Exfoliace“
Geben Sie eine Quelle nach APA, MLA, Chicago, Harvard und anderen Zitierweisen an
Machen Sie sich mit Top-50 Dissertationen für die Forschung zum Thema "Exfoliace" bekannt.
Neben jedem Werk im Literaturverzeichnis ist die Option "Zur Bibliographie hinzufügen" verfügbar. Nutzen Sie sie, wird Ihre bibliographische Angabe des gewählten Werkes nach der nötigen Zitierweise (APA, MLA, Harvard, Chicago, Vancouver usw.) automatisch gestaltet.
Sie können auch den vollen Text der wissenschaftlichen Publikation im PDF-Format herunterladen und eine Online-Annotation der Arbeit lesen, wenn die relevanten Parameter in den Metadaten verfügbar sind.
Sehen Sie die Dissertationen für verschiedene Spezialgebieten durch und erstellen Sie Ihre Bibliographie auf korrekte Weise.
1
Brodský, Jan. „Senzory plynů založené na 1D a 2D materiálech“. Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2021. http://www.nusl.cz/ntk/nusl-442589.
Der volle Inhalt der QuelleAnnotation:
In this work, general properties of fundamental gas sensors are described. Thesis is mainly focused on chemoresistive and ChemFET types, which are further used in experimental part. Subsequently, properties, preparation and transfer methods of chosen 1D and 2D materials are described. Experimental part of this work describes design and fabrication of chips, which combine the sensing principals mentioned above for utilization of 1D and 2D materials as an active layer. Transfer methods of individual materials on fabricated chips are described and these materials are characterized by Raman spectroscopy and field effect transistor characteristics measurements. Finally, the response of chosen materials to oxidative and reductive gases is measured.
2
Severa, Jiří. „Depozice Ga nanostruktur na grafenové membrány“. Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-443761.
Der volle Inhalt der QuelleAnnotation:
This diploma thesis deals with the preparation of the graphene membranes for depo-sition of gallium atoms by the molecular beam epitaxy. In the first part properties ofgraphene and methods of its production are described. Second part focuses on the gra-phene membranes, their specific properties, applications and methods of production. Thirdpart describes growth theory of the thin films. Practical part is focused on preparationof graphene membranes, which consists of covering the holes in the silicon substrate bygraphene layer. For that mechanical exfoliated and chemical vapor deposited graphenewere used. Subsequently, gallium atoms were deposited on these membranes by molecularbeam epitaxy and in situ observed by scanning electron microscopy.
3
Hrubý, Jakub. „Příprava a charakterizace hybridních materiálů na grafenové bázi“. Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2017. http://www.nusl.cz/ntk/nusl-318708.
Der volle Inhalt der QuelleAnnotation:
Grafen v kombinaci s komplexy kovů by mohl poskytnout nové přísutpy v hybridních materiálech založených na grafenové bázi a v oblasti molekulárního magnetismu. Obě témata jsou velmi diskutovaná jako taková, nicméně, výzkumu vedoucího k možnosti jejich míchání není mnoho. Vzorky byly připraveny sonikací grafitu v kapalné fázi, což vedlo k exfoliaci grafenu. Následně byly nadeponovány pomocí modiikované Lagmuirovy– Schaeferovy depoziční metody různé komplexy kovů na substrát pokrytý grafenem. Klíčovým krokem bylo určení vlastností takto připraveného materiálu. Proto byly následně vlastnosti takového hybridního materiálu charakterizovány pomocí vysokofrekvenční elektronové paramagnetické rezonance (angl. HFEPR), rastrovacího elektronového mikroskopu, (angl. SEM), Ramanovou spektroskopií a čtyř bodovou metodou měření odporu. V této práci jsme potvrdili naši presumpci, že je možné vytvořit hybridní materiál smícháním exfoliovaného grafenu s molekulárními magnety pro získání nových magnetických a elektronických vlastností, které by mohly být využity v další generaci detektorů a elektroniky.
4
Tesař, Jan. „Příprava a charakterizace atomárně tenkých vrstev“. Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-417143.
Der volle Inhalt der QuelleAnnotation:
Tato práce se zabývá oblastí dvourozměrných materiálů, jejich přípravou a analýzou. Pravděpodobně nejznámějším zástupcem dvourozměrných materiálů je grafen. Tento 2D allotrop uhlíku, někdy nazývaný „otec 2D materiálů“, v sobě spojuje neobyčejnou kombinaci elektrických, tepelných a mechanických vlastností. Grafen získal mnoho pozornosti a byl také připraven mnoha metodami. Jedna z těchto metod však stále vyniká nad ostatními kvalitou produkovaného grafenu. Mechanická exfoliace je ve srovnání s jinými technikami velmi jednoduchá, takto připravený grafen je však nejkvalitnější. Práce je také zaměřena na optimalizaci procesu tvorby heterostruktur složených z vrstev grafenu a hBN. Dle prezentovaného postupu bylo připraveno několik van der Waalsových heterostruktur, které byly analyzovány Ramanovskou spektroskopií, mikroskopií atomových sil a nízkoenergiovou elektronovou mikroskopií. Měření pohyblivosti nosičů náboje bylo provedeno v GFET uspořádání. Získané hodnoty pohyblivosti prokázaly vynikající transportní vlastnosti exfoliovaného grafenu v porovnání s grafenem připraveným jinými metodami. V práci popsaný proces přípravy je tedy vhodný pro výrobu kvalitních heterostruktur.
5
Wasala, KWM Milinda Prabath. „ELECTROCHEMICAL CHARACTERIZATION OF EXFOLIATED GRAPHENE“. OpenSIUC, 2014. https://opensiuc.lib.siu.edu/theses/1418.
Der volle Inhalt der QuelleAnnotation:
In this research we have investigated electrochemical and impedance characteristics of liquid phase exfoliated graphene electrodes. The exfoliated graphene electrodes were characterized in Electrochemical Double Layer Capacitors (EDLCs) geometry. Liquid phase exfoliation was performed on bulk graphite powder in order to produces few layer graphene flakes in large quantities. The exfoliation processes produced few layer graphene based materials with increased specific surface area and were found to have suitable electrochemical charge storage capacities. Electrochemical evaluation and performance of exfoliated graphene electrodes were tested with Cyclic Voltammetry, constant current charging discharging and Electrochemical Impedance Spectroscopy (EIS) at ambient conditions. We have used several electrolytes in order to evaluate the effect of electrolyte in charge storage capacities. Specific capacitance value of ~ 47F/g and ~ 262F/g was measured for aqueous and ionic electrolytes respectively. These values are at least an order of magnitude higher than those obtained by using EDLC's electrodes fabricated with the bulk graphite powder. In addition these EDLC electrodes give consistently good performance over a wide range of scan rates and voltage windows. These encouraging results illustrate the exciting potential for high performance electrical energy storage devices based on liquid phase exfoliated graphene electrodes.
6
Krejčí, Pavel. „Elektrochemická příprava grafen oxidu a jeho využití v elektrodových kompozitech s LiFePO4“. Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2018. http://www.nusl.cz/ntk/nusl-376908.
Der volle Inhalt der QuelleAnnotation:
This work deals with issues of application of the graphene material in the field of electrochemical energy storage. It includes basic graphene properties, the overview of methods for the production of lithium-iron-phosphate/graphene composites and results of different research approaches. The general aim is to present growing opportunity of application of graphene based composites in the electrochemical energy storage field. In the experimental part of this work, a electrochemical exfoliation of graphite and a production of LFP/G composites with different amount of graphene material and with different types of graphene material are carried out. This work includes also x-ray diffraction spectroscopy measurements and the evaluation of impacts of graphene additives on final properties of the electrochemical energy storage.
7
Abou-El-Nasr, Laila Ibrahim. „NMR study of ³He adsorbed on exfoliated graphite“. Thesis, Royal Holloway, University of London, 1989. http://repository.royalholloway.ac.uk/items/9cd869f5-18b2-431a-9ee4-19540aaa5e4e/1/.
Der volle Inhalt der QuelleAnnotation:
The present work has been carried out to investigate the dynamic properties of 3 He film adsorbed on an exfoliated graphite substrate, using pulsed NMR techniques. It has been found that the dipolar interaction is the dominant mechanism for the spin relaxation, although the effect of the grafoil local fields can not be ignored. The spin-lattice relaxation time T1 and the spin-spin relaxation time T2 which characterize the spin system were determined. The study has been concentrated on two phases. The registered phase and the solid phase. Some data were taken at the mixed phase which lies between them. Both relaxation times were determined as functions of monolayer capacity, frequency, temperature and spin orientations. For temperatures less than 2 K, the spins exhibit quantum motion behaviour. The frequency of this motion was determined and was found to be inversely proportional to the spin density. At the registered phase, the activation temperature was determined, where it was a maximum corresponding to perfect registry. Special attention was given to the T1 data at the minima in the solid phase since there the frequency of the motion is comparable to the Larmor frequency.
8
COISSARD, VERONIQUE. „Pemphigus foliace : a propos d'un cas d'erythrodermie exfoliante“. Nice, 1991. http://www.theses.fr/1991NICE6802.
Der volle Inhalt der Quelle
9
Kalaitzidou, Kyriaki. „Exfoliated graphite nanoplatelets as reinforcement for multifunctional polypropylene nanocomposites“. Diss., Connect to online resource - MSU authorized users, 2006.
Den vollen Inhalt der Quelle findenAnnotation:
Thesis (Ph. D.)--Michigan State University. Dept. of Chemical Engineering and Materials Science, 2006.Title from PDF t.p. (viewed on June 19, 2009) Includes bibliographical references. Also issued in print.
10
Islam, Md Akibul. „Characterization of Rapidly Exfoliated 2D Nanomaterials Obtained Using Compressible Flows“. University of Toledo / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1544704770760853.
Der volle Inhalt der Quelle
11
Zhang, Panpan, Sheng Yang, Roberto Pineda-Gómez, Bergoi Ibarlucea, Ji Ma, Martin R. Lohe, Teuku Fawzul Akbar, Larysa Baraban, Gianaurelio Cuniberti und Xinliang Feng. „Electrochemically Exfoliated High-Quality 2H-MoS₂ for Multiflake Thin Film Flexible Biosensors“. Wiley-VCH, 2019. https://tud.qucosa.de/id/qucosa%3A73171.
Der volle Inhalt der QuelleAnnotation:
2D molybdenum disulfide (MoS₂) gives a new inspiration for the field of nanoelectronics, photovoltaics, and sensorics. However, the most common processing technology, e.g., liquid‐phase based scalable exfoliation used for device fabrication, leads to the number of shortcomings that impede their large area production and integration. Major challenges are associated with the small size and low concentration of MoS₂ flakes, as well as insufficient control over their physical properties, e.g., internal heterogeneity of the metallic and semiconducting phases. Here it is demonstrated that large semiconducting MoS₂ sheets (with dimensions up to 50 µm) can be obtained by a facile cathodic exfoliation approach in nonaqueous electrolyte. The synthetic process avoids surface oxidation thus preserving the MoS₂ sheets with intact crystalline structure. It is further demonstrated at the proof‐of‐concept level, a solution‐processed large area (60 × 60 µm) flexible Ebola biosensor, based on a MoS₂ thin film (6 µm thickness) fabricated via restacking of the multiple flakes on the polyimide substrate. The experimental results reveal a low detection limit (in femtomolar–picomolar range) of the fabricated sensor devices. The presented exfoliation method opens up new opportunities for fabrication of large arrays of multifunctional biomedical devices based on novel 2D materials.
12
Sole, C. G. „Application of few layer graphene and exfoliated graphite materials in lithium ion batteries“. Thesis, University of Liverpool, 2017. http://livrepository.liverpool.ac.uk/3019844/.
Der volle Inhalt der Quelle
13
Cameron, Linda Margaret. „Kinetics of beta-carotene accumulatin and retention in exfoliated cells from supplemented individuals“. Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/27851.
Der volle Inhalt der QuelleAnnotation:
Human cancer intervention trials have found beta-carotene to be effective in reducing the genotoxic damage to oral mucosa cells that resulted from carcinogen exposure. Design of intervention trials using beta-carotene has so far lacked an important component, knowledge of the accumulation and retention of this putative chemopreventive agent in the tissues of interest. The factors of dose, timing of administration of supplements, and the effects of confounding factors are aspects of trial design that demand an understanding of the kinetics of beta-carotene in human tissues.
The oral mucosa is the only tissue so far that has been investigated for beta-carotene levels in exfoliated cells. A non-invasive technique for sample collection, suitable for sampling populations, in combination with a highly sensitive assay for beta-carotene, is appropriate for use with other epithelial sites that may be targets of intervention trials; one such site is the uro-genital tract.
This thesis describes preliminary investigations towards design of an intervention trial with beta-carotene directed at cells of the uro-genital tract.
Initial studies established the feasibility of measuring beta-carotene in uro-genital tract cells, and verified that the technical variation in the assays of oral mucosa cells and urogenital
tract cells was less than the variation between individuals in the study population.
A short-term (four-day) supplementation trial compared the effects of three doses of beta-carotene, given orally, on the beta-carotene content of exfoliated oral mucosa cells. Ingestion of 360 mg, 180 mg, and 90 mg of beta-carotene resulted in a rise in median cell beta-carotene levels from 1.8, 1.5, and 1.0 ng/10⁶ cells to 9.2, 7.7, and 3.9 ng/10⁶ cells, respectively, one week after the loading. Due to variation in response, the effects of the three doses were not significantly different from one another. The elevation in beta-carotene levels persisted for 2 weeks after the loading. The kinetic profile of the accumulation and retention of beta-carotene in uro-genital tract cells differed markedly from that of oral mucosa cells, in individuals who were supplemented for four weeks with a field trial dosage of beta-carotene. Median beta-carotene levels in uro-genital tract cells of beta-carotene-supplemented individuals increased from 0.6 ng/10⁶ cells to 2.8 ng/10⁶ cells during the loading period, a level significantly higher than that of the placebo group, but declined immediately after the end of the loading to levels that were not significantly elevated. In contrast, beta-carotene in exfoliated oral mucosa cells remained at significantly elevated levels until four weeks after the cessation of loading.
Tissue-specific features of beta-carotene accumulation in response to its administration need to be taken into consideration when designing intervention strategies that use beta-carotene.Medicine, Faculty of
Pathology and Laboratory Medicine, Department of
Graduate
14
Barrow, T. M. „The use of exfoliated cells to study the effect of diet upon the colon“. Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596429.
Der volle Inhalt der QuelleAnnotation:
This thesis investigates whether changes in colonic gene expression can be detected by the use of exfoliated cells, in the context of a study into the effect of a processed meat diet upon the colon. The yields of colonocytes and squamous cells from the stools of 16 healthy volunteers were established using cytokeratins 8 and 10 as markers of tissue lineage. Yields were insufficient for the purpose of studying gene expression at the mRNA level. RNA extraction directly from stool was observed to be highly degraded and displayed poor marker stability. Using a novel method of isolating exfoliated cells directly from the rectum (‘direct cell sampling’), colonocyte, yields were in the range of 103 – 104 cells, with little contamination by squamous cells or faecal debris. Few cells were observed to be proliferative, as determined by the absence of Ki67 and PCNA. RNA extracted from the cells showed satisfactory marker stability, with samples analysed in quadruplicate by qPCR displaying mean ranges of 0.72 and 1.03 in the Ct values for the β-actin and cytokeratin 8 genes. The approach was taken forward for validation against results from biopsies. To study the effect of a processed meat diet upon gene expression, biopsies were collected from 17 volunteers fed processed meat and vegetarian diets in a random cross-over design. For the validation of the direct cell sampling approach, exfoliated cells were collected from 7 volunteers for comparison. Microarray analysis performed on the biopsy samples revealed no differential gene expression between the diets. Stratification of the data set, to reduce variance, revealed increased expression of six inflammatory genes (CCL2, CCL18, CCL20, HBEGF, IL1B, VNN1) in response to the vegetarian diet. This unexpected finding requires further investigation.
15
Lu, Felix Paul. „Electrical characterization of thermally and mechanically exfoliated silicon films for flat panel display applications /“. Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2004. http://wwwlib.umi.com/cr/ucsd/fullcit?p3123654.
Der volle Inhalt der Quelle
16
Pilli, Srinivas. „Effects of ultrasonic impact treatment on fatigue life of pre-exfoliated AA-2024-T351“. Thesis, Sheffield Hallam University, 2008. http://shura.shu.ac.uk/20229/.
Der volle Inhalt der QuelleAnnotation:
In this study investigations were made into the effects of Ultrasonic Impact Treatment (UIT) on pre-exfoliated AA 2024 T351. Electrochemical tests were conducted to determine any changes in electrochemical behaviour of the alloys due to UIT condition. Uniaxial monotonic, cyclic and fatigue crack propagation (FCG) tests were conducted on material in As-Received (AR) condition and UIT condition in air and in a corrosive environment by pre-exfoliating the test specimens at pre-defined set of time periods and temperature range (20 °C). It was clear that the fatigue performance was severely reduced by the introduction of the corrosion environment for AR specimens. SEM analysis suggests that UIT conditioned AA 2024-T351 exhibits resistance to exfoliation corrosion at ambient and temperatures ranging between 20°C to 40°C when compared to AR specimens. However, these results are not supported by potentiodynamic polarisation curves which show a decrease in corrosion resistance of UIT specimens. Also it is understood that there is a considerable amount of Cu refinement and enrichment near the surface when the AA 2024-T351 is subjected to exfoliation corrosion tests. Whilst hydrogen is in an atomic state, it can be adsorbed onto the metal surface and consequently diffuses into the matrix and can have serious detrimental effects. A reference line for minimal pre-existing hydrogen in the alloy is identified and the magnitude of hydrogen is found to be 180 Arbitrary Hydrogen Units (AHU). It is also found that in corrosion environment, the hydrogen ingress and further charging is prominent at ambient temperatures for AR samples, and showed damage over the full width of cross-section. The following conclusions were drawn: 1. UIT surface treatments, followed by exfoliation corrosion have shown increased resistance to a reduction in mechanical properties, notably tensile and yield strength. Fractographic analysis further supported this finding by showing smaller average brittle failure depths for UIT specimens when compared to AR specimens. SEM analysis of AR samples (without exfoliation) showed a crystallographic contribution to the mode of failure where high density slip bands are formed and the initial failure exhibits a step format. 2. It is observed that during exfoliation, hydrogen ingress and adsorption is more prominent at ambient temperatures for AR samples. 3. A slight improvement In Low Cycle Fatigue (LCF) life is observed for pre-exfoliated and UIT conditioned sample but not for UIT conditioned samples only. Little effect is observed for either treatment in the High Cycle Fatigue (HCF) region. 4. Fatigue crack initiation occurred from the edges for all samples. 5. Fatigue crack propagation of exfoliated specimens exhibited faster crack propagation than As-Received specimens. UIT caused retardation in crack propagation rate in AR samples but not in corroded samples. Failure of pre-exfoliated, UIT treated samples failed within the treated strip. It is also noted that crack deviation can occur when the crack tip reaches a secondary phase particle. 6. Nanocrystallisation generates uniformity of the surface which refines the secondary phase particles and helps mitigate crack initiation sites.
17
Russell, Brice Adam. „Binary Gaseous Mixture and Single Component Adsorption of Methane and Argon on Exfoliated Graphite“. OpenSIUC, 2013. https://opensiuc.lib.siu.edu/theses/1334.
Der volle Inhalt der QuelleAnnotation:
Exfoliated graphite was used as a substrate for adsorption of argon and methane. Adsorption experiments were conducted for both equal parts mixtures of argon and methane and for each gas species independently. The purpose of this was to compare mixture adsorption to single component adsorption and to investigate theoretical predictions concerning the kinetics of adsorption made by Burde and Calbi.6 In particular, time to reach pressure equilibrium of a single dose at a constant temperature for the equal parts mixture was compared to time of adsorption for each species by itself. It was shown that mixture adsorption is a much more complex and time consuming process than single component adsorption and requires a much longer amount of time to reach equilibrium. Information about the composition evolution of the mixture during the times when pressure was going toward equilibrium was obtained using a quadrupole mass spectrometer. Evidence for initial higher rate of adsorption for the weaker binding energy species (argon) was found as well as overall composition change which clearly indicated a higher coverage of methane on the graphite sample by the time equilibration was reached. Effective specific surface area of graphite for both argon and methane was also determined using the Point-B method.2
18
Bento, Leticia Westphalen. „Mecanismos moleculares envolvidos na diferenciação das SHED (Stem Cells from Exfoliated Deciduous Teeth) em células endoteliais“. reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2012. http://hdl.handle.net/10183/63157.
Der volle Inhalt der QuelleAnnotation:
As células-tronco provenientes da polpa de dentes decíduos esfoliados (SHED) são uma fonte promissora de células-tronco para a terapia regenerativa. Já foi demonstrado que elas podem se diferenciar em células endoteliais, mas os mecanismos envolvidos nesse processo ainda são desconhecidos. Dessa forma, o presente estudo teve como objetivo elucidar os mecanismos moleculares relacionados à diferenciação endotelial dessas células. Para isso, um meio de cultura para células endoteliais (EGM-2MV), suplementado por 50ng/mL rhVEGF, foi utilizado com sucesso como estímulo para as SHED se diferenciarem em células endoteliais em cultura de monocamada. Uma vez que, elas expressaram os marcadores endoteliais VEGFR-2 e CD-31. Além disso, quando as SHED foram expostas ao meio de diferenciação, a fosforilação de STAT-3 (um marcador de células-tronco) foi inibida de acordo com a concentração utilizada, enquanto a fosforilação de ERK e AKT foi estimulada. Quando um inibidor de ERK foi adicionado ao meio, a fosforilação de STAT-3 aumentou. Por outro lado, quando um inibidor de STAT-3 foi adicionado ao meio de cultura, a fosforilação de ERK aumentou. A inibição de ERK também impediu a diferenciação endotelial. Para confirmar esse resultado, shRNA MEK-1 SHED também falharam em expressar VEGFR-2 quando estimuladas. Além disso, scaffolds de fatias dentais foram semeadas com shRNA VEGFR-1 SHED ou shRNA controle e implantadas no subcutâneo de camundongos imunodeficientes. Após recuperados, um tecido muito semelhante à polpa dental foi formado no interior das fatias. No entanto, havia menos células CD-31 positivas nos vasos sanguíneos dos implantes semeados com VEGFR-1 shRNA SHED, sugerindo um papel do VEGFR-1 na formação de vasos sanguíneos. Em conclusão, o VEGFR-1 e a via de sinalização de ERK estão envolvidos no processo de diferenciação das SHED em células endoteliais.Stem Cells from Exfoliated Deciduous Teeth (SHED) are a promising source of stem cells for regenerative therapy. It was already shown they can differentiate into endothelial cells, but the mechanisms involved in this process remain unclear. Therefore, the following study aimed to elucidate the molecular mechanisms related to endothelial differentiation of SHED. For this purpose, a culture media for endothelial cells (EGM-2MV), supplemented with 50ng/ml rhVEGF, was successfully used as stimuli for SHED to undergo endothelial differentiation in monolayer culture, as they expressed the endothelial markers VEGFR-2 and CD- 31. Moreover, when SHED were exposed to the differentiation medium, STAT-3 phosphorilation (a stemness marker) was inhibited while the ERK and AKT phosphorilation was stimulated. When an ERK inhibitor was added to the medium, the STAT-3 phosphorilation increased in a dependent concentration manner. On the other hand, when a STAT-3 inhibitor was added the ERK phosphorilation increased. The ERK inhibition also arrested endothelial differentiation. To confirm this results, shRNA MEK-1 SHED also failed to express VEGFR-2 when stimulated. Additionally, tooth slice scaffolds were seeded with shRNA VEGFR-1 SHED or shRNA control SHED and implanted, subcutaneously, into immunodeficient mice. After retrieved, a dental pulp-like tissue had been formed inside the tooth slice. However, there were fewer CD-31 positive blood vessels in the shRNA VEGFR-1 implants suggesting a role of VEGFR-1 in the formation of blood vessels by SHED. In conclusion, the VEGFR-1 and ERK pathway are involved in the process of differentiation of SHED into endothelial cells.
19
Jackson, Matthew V. „The Relationship between urinary 1-Hydroxypyrene and DNA Adducts in the exfoliated Bladder Cells of Firefighters“. University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1328298132.
Der volle Inhalt der Quelle
20
Sullivan, Erin M. „Understanding the process-structure-property relationship in biodegradable polymer nanocomposite films“. Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54428.
Der volle Inhalt der QuelleAnnotation:
The focus of this study was to explore process-structure-property relationships in biodegradable polymer nanocomposite films in order to eliminate the commonly used trial and error approach to materials design and to enable manufacturing of composites with tailored properties for targeted applications. The nanofiller type and concentration, manufacturing method and compounding technique, as well as processing conditions were systematically altered in order to study the process-structure-property relationships. Polylactic acid (PLA) was used as the polymer and exfoliated graphite nanoplatelets (GNP), carbon nanotubes (CNT), and cellulose nanocrystals (CNC) were used as reinforcement. The nanocomposite films were fabricated using three different methods: 1) melt compounding and melt fiber spinning followed by compression molding, 2) solution mixing and solvent casting, and 3) solution mixing and electrospinning followed by compression molding. Furthermore, the physical properties of the polymer, namely the crystallization characteristics were altered by using two different cooling rates during compression molding. The electrical response of the composite films was examined using impedance spectroscopy and it was shown that by altering the physical properties of the insulating polymer matrix, increasing degree of crystallinity, the percolation threshold of the GNP/PLA films is significantly reduced. Additionally, design of experiments was used to examine the influence of nanofiller type (CNT versus GNP), nanofiller content, and processing conditions (cooling rate during compression molding) on the elastic modulus of the composite films and it was concluded that the cooling rate is the primary factor influencing the elastic modulus of both melt compounded CNT/PLA and GNP/PLA films. Furthermore, the effect of nanofiller geometry and compounding method was examined and it was shown that the high nanofiller aspect ratio in the CNT/PLA films led to decreased percolation threshold compared to the GNP/PLA films. The melt compounded GNP/PLA films displayed a lower percolation threshold than the solution cast GNP/PLA films most likely due to the more homogeneous distribution and dispersion of GNP in the solution cast films. Fully biodegradable and biorenewable nanocomposite films were fabricated and examined through the incorporation of CNC in PLA. Through the addition of CNC, the degree of crystallinity of the matrix was significantly increased. Focusing the design space through investigation of process-structure-property relationships in PLA nanocomposites, can help facilitate nanocomposites with tailored properties for targeted applications.
21
Cardenas, Abastos Paloma Fernanda, Chinchay Arturo Fernández, Cáceres Sofia Puscan, Del Castillo Eliot Gabriel Rojas und Vilchez Camila Alexandra Rosado. „Proyecto: Línea de exfoliante facial y corporal orgánicos a base de guayaba y semillas de sacha inchi“. Bachelor's thesis, Universidad Peruana de Ciencias Aplicadas (UPC), 2020. http://hdl.handle.net/10757/655097.
Der volle Inhalt der QuelleAnnotation:
Se desarrolló el proyecto Añay Care, empresa que se dedica a la producción de exfoliantes faciales y corporales a base los frutos exóticos del Perú (Pitaya, Aguaje y Acaí) con semillas de Sacha Inchi, con enfoque al segmento del SKYNCARE. En primer término, se mostrará los aspectos cualitativos y cuantitativos para su respectivo análisis. Consecuentemente, la elaboración de las proyecciones financieras a partir de las inversiones, ingresos, costos y gastos que se va a desarrollar en los próximos tres años. Así mismo, debido a diferentes fuentes se ha proyectado la participación de mercado que podrá obtener a nivel nacional.
Se validó el modelo de negocio por medio de la elaboración de la herramienta Business Model Canvas, Valué Proposición Canvas y a través de encuestas para validar la hipótesis y mejorar los MVPs (Producto Mínimo Viable). Así mismo, la empresa ha incurrido en gastos preoperativos en activos tanto tangibles como intangibles.
Se resalta como ventaja competitiva, la adquisición de insumos naturales los cuáles son comprados a las comunidades campesinas del Perú, pues existe el compromiso con su desarrollo por lo que están incluidos en nuestro plan de responsabilidad social, así como todos nuestros stakeholders. Para finalizar, se puede indicar que gracias al valor que aporta y a la participación creciente que se obtendrá se concluye que será un proyecto viable. Finalmente, se evaluará los aspectos financieros a través del desarrollo del Flujo de Caja Libre, Estado de Resultados, CTN, VAN, Punto de equilibrio dentro de los 3 años proyectados.The Añay Care project was developed, a company that is dedicated to the production of facial and body scrubs based on exotic fruits from Peru (Pitaya, Aguaje and Acaí) with Sacha Inchi seeds, with a focus on the SKYNCARE segment. In the first place, the qualitative and quantitative aspects will be shown for their respective analysis. Consequently, the preparation of financial projections based on investments, income, costs, and expenses that will be developed in the next three years. Likewise, due to different sources, the market share that it will be able to obtain at the national level has been projected. The business model was validated through the development of the Business Model Canvas tool, Valué Proposition Canvas and through surveys to validate the hypothesis and improve the MVPs (Minimum Viable Product). Likewise, the company has incurred pre-operating expenses in both tangible and intangible assets. The acquisition of natural inputs is highlighted as a competitive advantage, which are purchased from the peasant communities of Peru, since there is a commitment to their development, which is why they are included in our social responsibility plan, as well as all our stakeholders. Finally, it can be indicated that thanks to the value it contributes and the increasing participation that will be obtained, it is concluded that it will be a viable project. Finally, the financial aspects will be evaluated through the development of the Free Cash Flow, Income Statement, CTN, NPV, Break-even point within the projected 3 years.
Trabajo de investigación
22
Li, Hongyan, Yang Hou, Faxing Wang, Martin R. Lohe, Xiaodong Zhuang, Li Niu und Xinliang Feng. „Flexible All-Solid-State Supercapacitors with High Volumetric Capacitances Boosted by Solution Processable MXene and Electrochemically Exfoliated Graphene“. Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2018. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-235446.
Der volle Inhalt der Quelle
23
Neff, David N. „Integrated Bipolar Plate – Gas Diffusion Layer Design for Polymer Electrolyte Membrane Fuel Cells“. Wright State University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=wright1261092610.
Der volle Inhalt der Quelle
24
Twumasi, Sylvester Kwadwo. „Catalytic investigations of CO and NO reactions applying exfoliated graphite intercalation compounds of AlCl3, CuCl2, MoOCl3, FeCl3 and Ce(IV)nitrate“. [S.l. : s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=96423825X.
Der volle Inhalt der Quelle
25
Yamada, Hitoshi. „Detection of tumor-derived DNA in exfoliated cells of urine sediments with a novel quantitative PCR method based on allele-specific PCR“. Kyoto University, 1999. http://hdl.handle.net/2433/181733.
Der volle Inhalt der Quelle
26
Carvalho, Cristiane Alves Paz de. „Frequência de micronúcleos em células esfoliadas da mucosa bucal de pacientes obesos“. Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/25/25150/tde-05112012-214733/.
Der volle Inhalt der QuelleAnnotation:
A crescente incidência da obesidade e suas comorbidades constituem-se em um grande desafio para a saúde no mundo. Além da doença cardiovascular e do diabetes, dados epidemiológicos demonstraram ligação entre a obesidade e diversos tipos de câncer. As alterações citogenéticas tem sido utilizadas como biomarcadores para identificação de danos celulares. Este estudo teve como objetivos: comparar a frequência dos tipos celulares (células basais e diferenciadas), anormalidades nucleares (células binucleadas, picnóticas, cariorréticas, cariolíticas e com cromatina condensada) e de danos celulares (micronúcleos e brotos nucleares) de células bucais esfoliadas em um grupo de obesos (teste) e em um grupo de indivíduos com peso normal (controle). A amostra foi composta por 30 indivíduos, sendo o grupo teste constituído por indivíduos obesos mórbidos (n=15) e o grupo controle por indivíduos com peso normal (n=15). A classificação do peso corporal foi feita de acordo com o Índice de Massa Corporal (IMC); um questionário forneceu informações sobre exposições ocupacionais e não ocupacionais; hábitos e dieta. As células da mucosa bucal foram coletadas da mucosa jugal, de ambos os lados, processadas e analisadas microscopicamente. Para cada indivíduo foram avaliadas 1000 células para a caracterização dos tipos celulares (basal e diferenciada) e alterações nucleares (células binucleadas, picnose, cariólise, cariorrexe, cromatina condensada) e 2000 células diferenciadas para verificar a presença de danos celulares (micronúcleos e brotos nucleares). Os dados foram processados e analisados estatisticamente, por meio do teste de Mann Whitney. Considerou-se o nível de significância de 5% (p<0,05). Observaram-se diferenças nas frequências de tipos celulares e anomalias nucleares para os dois grupos, porém estas diferenças não foram significativas (p>0,05). Quanto ao tipo de dano celular, notou-se a mesma frequência de brotos nucleares para ambos os grupos, entretanto, a frequência de micronúcleos foi maior para o grupo obeso (p<0,001). Neste estudo, verificou-se maior frequência de micronúcleos nas células esfoliadas da mucosa bucal em indivíduos obesos mórbidos que em indivíduos com peso normal. Este achado sugere que a obesidade possa levar à maior ocorrência de alterações citogenéticas.The increasing incidence of obesity and its co-morbid conditions poses a great challenge to global health. In addition to cardiovascular disease and diabetes, epidemiological data demonstrate a link between obesity and multiple types of cancer. The buccal micronucleus cytome assay has been used as a biomarker for identification of cell damage. This study aimed to compare the frequency of cell types (basal and differentiated), nuclear anomalies (binucleated, pyknotic, karyorrhectic, karyolitic and condensed chromatin cells), and cell damage (micronuclei and nuclear buds) in exfoliated buccal cells in a group of obese (test) and a group of normal weight (control).The sample consisted of 30 subjects, the test group comprised of individuals with morbid obesity (n = 15) and a control group of normal weight (n = 15). The classification of body weight was made according to Body Mass Index (BMI), a questionnaire provided information on occupational exposures and non-occupational, lifestyle and diet. The oral mucosa cells were collected from the buccal mucosa, on both sides, processed and analyzed microscopically. For each individual 1000 cells were evaluated for the characterization of cell types (basal and differentiated) and nuclear abnormalities (binucleated cells, pyknosis, karyolysis, karyorrhexis, condensed chromatin) and 2000 differentiated cells for the presence of cellular damage (micronuclei and nuclear buds). The data were processed and statistically analyzed using the Mann-Whitney test. We considered the significance level of 5% (p <0.05). Differences were observed in the frequencies of cell types and nuclear abnormalities in both groups, but these differences were not significant (p> 0.05). Regarding the type of cell damage, we noticed the same frequency of nuclear buds for both groups, however, the frequency of micronuclei was higher in the obese group (p <0.001). In this study, there was a higher frequency of micronuclei in exfoliated cells of buccal mucosa in morbidly obese individuals than in individuals with normal weight. This finding suggests that obesity may lead to higher rates of cytogenetic changes.
27
Rosario, Astrid Christa. „The Chemistry of Dimethacrylate-Styrene Networks and Development of Flame Retardant, Halogen-Free Fiber Reinforced Vinyl Ester Composites“. Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/11228.
Der volle Inhalt der QuelleAnnotation:
One of the major classes of polymer matrix resins under consideration for structural composite applications in the infrastructure and construction industries is vinyl ester resin. Vinyl ester resin is comprised of low molecular weight poly(hydroxyether) oligomers with methacrylate endgroups diluted with styrene monomer. The methacrylate endgroups cure with styrene via free radical copolymerization to yield thermoset networks. The copolymerization behavior of these networks was monitored by Fourier Transform Infrared Spectroscopy (FTIR) at various cure conditions. Reactions of the carbon-carbon double bonds of the methacrylate (943 cm-1) and styrene (910 cm-1) were followed independently. Oligomers possessing number average molecular weights of 700 g/mole were studied with systematically increasing levels of styrene. The Mortimer-Tidwell reactivity ratios indicated that at low conversion more styrene was incorporated into the network at lower cure temperatures. The experimental vinyl ester-styrene network compositions deviated significantly from those predicted by the Meyer-Lowry integrated copolymer equation at higher conversion, implying that the reactivity ratios for these networks may change with conversion. The kinetic data were used to provide additional insight into the physical and mechanical properties of these materials.
In addition to establishing the copolymerization kinetics of these materials, the development of halogen free fiber reinforced vinyl ester composites exhibiting good flame properties was of interest. Flame retardant vinyl ester resins are used by many industries for applications requiring good thermal resistance. The current flame-retardant technology is dependent on brominated vinyl esters, which generate high levels of smoke and carbon monoxide. A series of halogen free binder systems has been developed and dispersed in the vinyl ester to improve flame retardance. The binder approach enables the vinyl ester resin to maintain its low temperature viscosity so that fabrication of composites via Vacuum Assisted Resin Transfer Molding (VARTM) is possible. The first binder system investigated was a polycaprolactone layered silicate nanocomposite, which was prepared via intercalative polymerization. Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD) data indicated a mixed morphology of exfoliated and intercalated structures. The mechanical properties and the normalized peak heat release rates were comparable to the neat vinyl ester resin.
Alternative binder systems possessing inherent flame retardance were also investigated. A series of binders comprised of novolac, bisphenol A diphosphate, and montmorillonite clay were developed and dispersed into the vinyl ester matrix. Cone calorimetry showed reductions in the peak heat release rate comparable to the brominated resin.Ph. D.
28
Juhlin, Stina. „Evaulation of liquid-exfoliatedgraphene as additive in Ag-basedsliding contacts“. Thesis, Uppsala universitet, Tillämpad materialvetenskap, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-353942.
Der volle Inhalt der QuelleAnnotation:
This master thesis work is performed at ABB Corporate Research Center inVästerås. The aim of this study is to investigate Ag:graphene composites as slidingelectrical contacts, suitable for use in e.g. tap-changers. Three different graphenematerials, all produced by a low-cost exfoliation process, are evaluated in this study. The results are compred to an ongoing work on Ag:GO (graphene oxide) composites. This material has shown very good tribological properties, however it hasbeen difficult to handle during sintering processing. The goal of this study is to geteven better tribological, electrical and mechanical properties than Ag:GO, and also todevelop a new powder-metallurgical method to produce the Ag:graphene composites.The study also investigates the influence of graphene flake size and concentration aswell as microstructure of the Ag:graphene composites. This report focuses on aninvestigation of the graphene raw material quality from the suppliers, and friction,wear and resistance analysis of the composites. This is done by using Ramanspectroscopy, SEM with EDS, LOM, tribometer tests and resistivity analysis. Raman and SEM analyses show that none of the supplied LEG materials are ofhigh-quality G (single or bilayer), but rather multi-layer graphene or even graphite.Small amounts of graphene added to Ag gave extremly low friction (μ<0.2 vs. pureAg μ~1.3, 5 N load and 5 cm/s speed). The composite manufacturing process hadcritical steps, which have to be optimized, to obtain low values of friction. Severedegassing of the composites was observed for some sampes, but the samples stillmaintained good friction values. SEM and EDS analyses of 2dfab’s wear track show abuild-up thin carbon-containing tribofilm on the Ag surface. Indicating that G ispresent, and works as a lubricant, creating good tribological properties. The resultsfrom this project may for sure be of importance for future ABB products in specificindustrial applications.
29
Soltani, Paniz. „Synthesis of novel carbon materials for supercapacitor applications“. Master's thesis, Universidade de Aveiro, 2017. http://hdl.handle.net/10773/22368.
Der volle Inhalt der QuelleAnnotation:
Mestrado em Química - Química Inorgânica e MateriaisMicro-supercapacitors (MSCs) are the key components of miniaturized, portable and wearable electronic devices. Although many advances have been made in this field during the recent years, micro-supercapacitors energy density remains far from those from lithium-ion batteries and electrolyte capacitors. Many efforts have been made to improve MSCs performances such as fabrication of nanostructures and thin-film manufacture technologies. Here, we demonstrated MSCs based on porous carbon and PEDOT: PSS polymer as well as RuO2 and electrochemically exfoliated graphene. Combining materials with pseudo capacitive and electrochemical double layer capacitance ability, the resulting MSCs deliver an area capacitance up to 1mFcm-2 and stack capacitance up to 51 Fcm-3 for graphene based devices and area capacitance up to 203 μFcm-2 and stack capacitance up to 12 Fcm-3 for polymer based devices. Both devices show ability to be operated in ultra-high rates up to 1000 Vs-1 which is around three orders of magnitude higher that of conventional batteries. The high capacitance is generally obtained at low scan rates (~ 10 mVs-1) and 40% of capacitance retention has been observed.
Micro-supercondensadores (MSCs) são os principais componentes de dispositivos eletrónicos miniaturizados, portáteis e utilizáveis no vestuário. Embora muitos avanços tenham sido feitos neste campo nos últimos anos, a densidade de energia dos micro-supercondensadores permanece aquém das baterias de iões de lítio e dos condensadores eletrolíticos. Muitos esforços foram feitos para melhorar os desempenhos dos MSCs, como e fabricação de nanoestruturas e as tecnologias de filmes finos. Neste trabalho estudam-se MSCs baseados em carbono poroso e PEDOT:PSS, bem como de RuO2 e grafeno electroquimicamente exfoliado. A combinação de materiais com capacitância de camada dupla pseudo-capacitiva e eletroquímica permite obter MSCs com uma capacitância até 1 mF.cm-2 e capacidade até 51 F.cm-3 nos dispositivos baseados em grafeno e capacitância até 203 μF.cm-2 e capacitância de 12 F.cm-3 nos dispositivos baseados em polímero. Ambos os dispositivos podem ser operados até 1000 V.s-1, um valor cerca de três ordens de grandeza maior do que o das baterias convencionais. A elevada capacitância foi obtida com baixas taxas de varrimento (~ 10 mV.s-1) com retenção de aproximadamente 40%.
30
Rodrigues, Pedro António Veiga. „Estudos de dispersão de nanografite em polipropileno“. Master's thesis, 2015. http://hdl.handle.net/1822/39537.
Der volle Inhalt der QuelleAnnotation:
Dissertação de mestrado integrado em Engenharia de MateriaisNo presente trabalho foram estudados os mecanismos de dispersão e reaglomeração de nanocompósitos de polipropileno (PP) /grafite exfoliada na composição e no processamento por extrusão. A composição foi realizada numa mini-extrusora de duplo-fuso com três zonas de mistura intensiva constituídas por elementos de mistura (kneading blocks) separadas por zonas de transporte. Procedeu-se à composição de nanocompósitos de PP com 2% ou 10% (p/p) de grafite GnP C ou grafite GnP H, e o seu posterior processamento numa mini-extrusora de mono-fuso, utilizando duas velocidades de rotação do parafuso. A evolução da dispersão ao longo das duas extrusoras foi analisada por microscopia ótica de campo claro. Também foram estudados o efeito da funcionalização via cicloadição dipolar 1,3 das grafites ligadas covalentemente ao PP enxertado com anidrido maleico (PP-g-AM), bem como as propriedades elétricas dos nanocompósitos. Na etapa de composição, observou-se o decréscimo significativo no tamanho e na quantidade dos aglomerados de grafite na passagem pela primeira zona de mistura intensiva, demonstrando a sua ação eficaz. A dispersão ao longo da mini-extrusora revelou-se constante após a primeira zona. No entanto, a funcionalização da grafite GnP C revelou um aumento da dispersão contínuo até à cabeça de extrusão. Os níveis de dispersão da grafite GnP H funcionalizada foram muito similares às da não-funcionalizada. No processamento, observou-se uma tendência geral de aumento da quantidade de aglomerados visíveis, indicando reaglomeração, independentemente da velocidade de processamento. Esta reaglomeração foi menos expressiva para os nanocompósitos com grafite funcionalizada. A dispersão foi aumentando ao longo da mini-extrusora, sendo o aumento maior para a velocidade mais elevada. A morfologia final dos nanocompósitos processados apresenta um nível de dispersão menor do que a resultante da composição. Simultaneamente, verificou-se um aumento da condutividade elétrica após o processamento. Nos nanocompósitos de PP com grafite GnP C, a funcionalização resultou numa menor condutividade, uma vez que induziu níveis de dispersão maiores.
The present work reports the study on the mechanisms of dispersion of exfoliated graphite/ polypropylene nanocomposites upon melt compounding and extrusion. Compounding was performed in a mini twinscrew extruder containing three intensive mixing zones consisting of kneading blocks. PP with 2wt. % or 10wt. % of GnP C or GnP H were compounded and subsequently processed by a mini single-screw extruder using two different screw speeds. The evolution of dispersion throughout compounding and processing was analysed by optical microscopy. The effect of graphite functionalization via 1,3 dipolar cycloaddition grafted with PP-g-MA (PP grafted with maleic anhydride) was also studied, as well as the electrical properties of the nanocomposites. The first set of kneading blocks were effective in decreasing the number and size of the graphite agglomerates. The dispersion along the mini-extruder proved to be constant after the first zone. However, functionalization of graphite GnP C revealed an increase in dispersion. The dispersing levels of as received and functionalized graphite GnP H were very similar, indicating that this kind of functionalization had no significant impact on dispersion. Along extrusion, the amount of agglomerates increased, indicating re-agglomeration of graphite agglomerates, regardless of processing speed. This re-agglomeration was less pronounced for nanocomposites with functionalized graphite. The final morphology of processed nanocomposites is coarser in comparison with composition. Concerning the electrical properties, there was an increase in conductivity of several orders of magnitude after processing. In the case of nanocomposites with GnP C graphite, functionalization induced lower conductivity, since it resulted in higher levels of dispersion.
31
An-Ting, Chien. „Study on Polymer/Exfoliated Montmorillonite Nanocomposites“. 2006. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-0311200617315600.
Der volle Inhalt der Quelle
32
Lo, Tzu-Sen, und 羅子森. „Physical Properties of Exfoliated Graphite Composites“. Thesis, 2011. http://ndltd.ncl.edu.tw/handle/41829447710098171570.
Der volle Inhalt der QuelleAnnotation:
博士逢甲大學
機械與航空工程研究所博士班
99
Three sets of expanded graphite filled polymers, having three different particle sizes, were reinforced with 1–5% by weight. The structural, mechanical and electrical properties of these composites were studied and compared. After dispersion, the particles were reduced to nanometer size through exfoliation, sonication, and high-shear strain rate mixing, which further breaks and delaminates them. In addition, scanning electron microscope characterizations were performed. The expanded graphite filled polymer material could be tailored to be high conducting. Compared with the pure polymer, the polymers filled with 5% wt. expanded graphite significantly reduce the electrical resistivity by orders. Compression, three-point-bending and impact tests were conducted. The influence of dispersion on the material behavior was studied. Some fracture modes associated with the layered microstructures of the graphite nanosheets were observed.
33
Chien, An-Ting, und 簡安廷. „Study on Polymer/Exfoliated Montmorillonite Nanocomposites“. Thesis, 2006. http://ndltd.ncl.edu.tw/handle/04366418150558980148.
Der volle Inhalt der QuelleAnnotation:
碩士國立臺灣大學
高分子科學與工程學研究所
95
A series of partial and fully water-soluble monomers, including methyl methacrylate, methyl acrylate, vinyl acetate, acrylamide, and glycidyl methacrylate, were used to fabricate polymer-Montmorillonite(MMT) nanocomposite through soap-free emulsion polymerization or solution polymerization, while MMT was intercalated by potassium persulfate(KPS) initiator in advance. Due to the confined space of clay interlayer regions, the polymerizing chains were aggregated into a disk-like or irregular domain depending on their intrinsic properties. The growing domains would trigger the exfoliation of MMT, and further polymerization afforded the latex particles of Polymer-MMT nanocomposites. In addition, for fully water soluble monomer, such as acrylamide, the growing chain would also exfoliate MMT. However, they formed a hydrogel system with dispersed exfoliated MMT nanoplatelets. In brief, the exfoliated polymer-MMT nanocomposite could be fabricated from partial or fully water-soluble monomers through polymerization in the interlayer regions of MMT. In order to study the effect of dispersed MMT nanoplatelets on the properties of polymers, exfoliated poly(vinyl acetate)-montmorillonite (PVAc-MMT) nanocomposite films and crosslinked poly(vinyl acetate- Glycidyl methacrylate)-montmorillonite (PVAc-GMA-MMT) crosslinked nanocomposite films were fabricated for further analysis. These transparent smooth films performed many superior properties, such as mechanical properties, vapor barrier properties, chemical resistance and fire retardation. In conclusion, MMT nanoplatelets acted as nano-size scaffolds in the nanocomposite structure to improve physical properties.
34
Wang, Li-Hsun, und 王儷勳. „Applications of Exfoliated Montmorillonite on Sunscreen Formulations“. Thesis, 2011. http://ndltd.ncl.edu.tw/handle/66919597398072578069.
Der volle Inhalt der QuelleAnnotation:
碩士國立臺灣大學
材料科學與工程學研究所
99
Sunscreen contains both organic and inorganic active ingredients. The organic active ingredient such as para-aminobenzoic acid (PABA) can produce several reactive intermediates under sunlight, and inorganic active ingredients, such as titanium dioxide and zinc oxide, are a well-known semiconductor with photocatalytic properties. When titanium dioxide and zinc oxide are combined with organic filters in sunscreen formulation, they would act as a photocatalyst to accelerate the degradation of organic molecules. To reduce the above-mentioned undesired side effects from UV Sunscreens, we employed the exfoliated montmorillonite(exMMT) as the sunscreen ingredient and investigated its effect on the degradation of organic ingredients and possible protection for the humanskin under UV irradiation. The experimental results show that the presence of titanium dioxide (TTO and TiO2 Rod) and zinc oxide (ZnO) could increase the UV-vis absorption of PABA at ultraviolet region, but exMMT decreased the UV-vis absorption at 304 nm. All these four ingredients have the catalytic effect on the photochemical reaction of PABA, especially titanium dioxide. The presence of exMMT and titanium dioxide nanoparticles (TTO and TiO2 Rod) could also increase the PL intensities of PABA at 347nm. Besides, the formation of PABA dimer and aggregation adsorbing on TTO and TiO2 Rod caused a red shift of PL spectrum. Moreover, ZnO could be excited by the emission light from PABA at 347nm and emitted another peak at 386 nm. To analyze the effect of sunscreen lotion on the changes of pig skin tissue after exposure to UV light, we wiped the sunscreen lotion on pigskin and exposed it to the UV irradiation, which was then subjected to measure the IR spectra by ATR-FTIR. The results showed that for the pristine pigskin, the intensities of characteristic peaks of lipids such as of -C=O at 1745cm-1, -CH3 at 1366cm-1 and C-O at 1164cm-1 decreased with increasing the intensity of 1260cm-1, which has been attributed to the formation of peroxide groups from the peroxidative damage of lipids. The intensities of the characteristic peaks related to the proteins such as amide Ⅱ at 1539cm-1 and -COO non-symmetric stretching vibration at 1574cm-1 decreased with increasing the intensity of 3280cm-1from NH2. As to the characteristic peaks related to DNA, PO2- asymmetric vibration at 1231cm-1 decreased, whereas PO2-symmetric vibration at 1095cm-1 increased. Interestingly, after applying the sunscreen containing the individual PABA, TiO2, ZnO, and their conbinations, the intensity of 1260cm-1 related to the lipid peroxidation weakened, whereas the characteristic peaks of protein and DNA were barely changed compared to the pristine pigskin. When the exMMT was included in the formulation of sunscreen, it significantly hindered the lipid peroxidation along with increasing the intensities of C=O peak and decreasing the intensity of NH2 peak under UV irradiation.
35
Hung, Chen-Ting, und 洪振庭. „Fabrication and Electrical Properties of Exfoliated Graphite“. Thesis, 2007. http://ndltd.ncl.edu.tw/handle/02885336052453011596.
Der volle Inhalt der QuelleAnnotation:
碩士逢甲大學
航太與系統工程所
95
In this thesis, we employed three-electrode electrochemical system and electrochemical half-cell to measure the Galvan static charge and discharge based on the exfoliated graphite (EG). Measurements were taken on the capacitance of uncompressed, compressed, sonicated, and unsonicated samples. In the other experiment, the EG was mixed with epoxy resin to produce composites, and measured the radar absorptive in the frequency ranges of 6-15 GHz by waveguide resonator. Then we examined the effect of the radar absorption with the different content of EG (with EG weight percentage 0%-5%) and the different thickness of the samples (1, 2, 2.5, 3 mm). The experimental data shows that the capacitance of the uncompressed samples is 50 times higher than the capacitance of the compressed samples. The efficiency of the sonicated and compressed samples is better than those without sonication. But the efficiency of the sonicated and uncompressed samples is lower than it was not sonicated. In the other experiment, we know that this type of composite is unable to absorb electromagnetic wave effectively. No matter what we changed the content of EG or the thickness of the samples, it can’t increase the radar absorption significantly in this research.
36
Peixoto, Hélder Xavier Pereira. „Optical characterization of black phosphorus exfoliated crystals“. Master's thesis, 2015. http://hdl.handle.net/1822/44399.
Der volle Inhalt der QuelleAnnotation:
Dissertação de mestrado em Física (área de especialização em Física Aplicada)Graphene and semiconducting few layer transition metal dichalcogenides are the two-dimensional (2D) materials most intensively studied in recent years. Recently, Black Phosphorus emerged as a new 2D material with many remarkable properties such as its widely tunable direct bandgap, high charge carrier mobility and high in-plane anisotropic electrical, optical and phonon prop- erties. In this thesis we propose an experimental characterization of the material along with com- putational calculations using Density Functional Theory. Spectroscopic transmission nulling ellipsometry was used to study birefringence and linear dichroism, while reflection nulling el- lipsometry was used to study the dielectric function. New ways of obtaining crystal orientation and thickness are presented. To find and characterize thin BP flakes, photoluminescence, ra- man, AFM and optical microscopy were employed. As the material degrades quickly in ambient conditions, a new encapsulation method was successfully introduced and tested. Answering the demand of obtaining large few layer areas, laser thinning was proposed. High dichroism and birefringence were observed and quantified. These two properties can be important for optical devices designing in the future. The laser thinning procedure was shown to be an effective way to produce large areas of few layer BP, which may be important in future, as such areas in their natural way are difficult to be identified.
O grafeno e as monocamadas de dicalcogenetos de metais de transição têm sido os materials bidimensionais mais intensamente estudados nos últimos anos. Recentemente, o Black Phos- phorus (também conhecido como fosforeno, na configuração de poucas camadas) foi exfoliado até uma única camada atómica, emergindo assim como um novo material 2D com propriedades excecionais tais como o band gap variável, a alta mobilidade dos portadores de carga e uma elevada anisotropia nas suas propriedades elétricas, óticas e fonónicas. Neste trabalho é apresentada uma caracterização experimental de propriedades óticas do material, assim como simulações computacionais usando Teoria do Funcional da Densidade (DFT). Foi usada elipsometria espetroscópica com o procedimento nulling. Foram efectuadas medidas em transmissão, com o objectivo de caracterizar a birrefringência e o dicroísmo linear, enquanto que o modo de reflexão foi usado para estudar a função dielétrica. Novas formas de obter a orientação dos eixos do cristal e de determinar a espessura são também apresentadas. De um modo geral, fotoluminescência, raman, microscopia de força atómica e microscopia ótica foram usadas para caracterizar o material. Uma vez que o material se degrada rapidamente nas condições ambiente, uma nova forma de encapsulamento e protecção é apresentada. Para além disso, de forma a responder à procura por grandes áreas com monocamadas ou camadas muito finas do material, laser thinning foi proposta como uma forma de produzir estas regiões. Foi observada e quantificada uma elevada birrefringência, bem como elevado dicroísmo. Estas duas propriedades podem ser importantes para a futura concepção de dispositivos ópti- cos com este material. O procedimento de laser thinning revelou também a possibilidade de obtenção de poucas camadas de BP em grandes áreas, o que se revela importante, na medida em que a identificação destas regiões, na sua forma natural, é bastante difícil.
37
Chen, Chia-Chi, und 陳佳琪. „Environmental transformations of exfoliated molybdenum disulfide sheets“. Thesis, 2019. http://ndltd.ncl.edu.tw/cgi-bin/gs32/gsweb.cgi/login?o=dnclcdr&s=id=%22107NCHU5087039%22.&searchmode=basic.
Der volle Inhalt der QuelleAnnotation:
碩士國立中興大學
環境工程學系所
107
Applications of transition metal dichalcogenide (TMDs) nanosheets with different elemental compositions have attracted growing attention in various fields. However, these materials have not been well-regulated due to the knowledge gap of their behaviors and impacts on the recipient environment. Therefore, a thorough investigation of the behaviors and interactions with environmental mediators can help to assess and predict the possible fate, transport, and toxicity of nanosheets. In the present study, chemically exfoliated (ceMoS2) and surfactant dispersed molybdenum disulfide nanosheets (sMoS2) were fabricated to serve as representative TMDs materials. The chemical stability of molybdenum disulfide and interactions with other environmental constituents were studied, and the interactions between NOM and various surfactants under environmentally relevant conditions were explored. The results indicate that in the dark ambient environment, sMoS2 shows greater stability compared to ceMoS2, which suggests that the surface coating can effectively inhibit the aging of MoS2. In the presence of ALHA and SRNOM, the oxidative degradation of ceMoS2 is significantly retarded. In the light-irradiated environment condition, ALHA promotes the degradation of ceMoS2, while SRNOM efficiently suppresses the oxidation of molybdenum disulfide nanosheets and inhibits the metal dissolution. Additionally, surface coating by different types of surfactants enhances the stability of sMoS2 to a varying degree. Overall, the results serve to provide insights to understand the behavior and transformation of TMDs nanosheets in natural systems and to explore the mechanisms involved.
38
Miranda, Sónia Daniela Ferreira. „Produção de filamentos compósitos de poliestireno-grafite exfoliada“. Master's thesis, 2018. http://hdl.handle.net/1822/64965.
Der volle Inhalt der QuelleAnnotation:
Dissertação de mestrado integrado em Engenharia de PolímerosA nanotecnologia tem vindo progressivamente a encontrar mais aplicações em diversas áreas. A utilização de nanocompósitos, em particular, permite produzir materiais com propriedades elevadas que não seriam possíveis com o polímero apenas, com a adição de uma pequena quantidade do nanomaterial de reforço. As propriedades dos nanocompósitos poliméricos dependem da forma como estes são preparados. Ao produzi-los é necessário assegurar que é alcançada uma boa dispersão e distribuição de nanopartículas por toda a matriz polimérica, e que estabelece uma boa interface com o polímero. Algumas das nanopartículas que têm despertado interesse científico são os alótropos do carbono, tais como os nanotubos de carbono, grafeno e grafite. No presente trabalho estudou-se o efeito da introdução de grafite exfoliada nas propriedades de compósitos com poliestireno. Assim, foram preparados compósitos de Poliestireno (PS) com grafites exfoliadas (EG) e funcionalizadas quimicamente, com diferentes composições. Estes nanocompósitos foram posteriormente extrudidos na forma de filamentos. Os filamentos obtidos foram caraterizados em termos de diâmetro, quanto à sua morfologia, dispersão das nanopartículas, resistividade elétrica, caraterísticas térmicas e propriedades mecânicas. Neste trabalho foi possível produzir filamentos compósitos cilíndricos com diâmetro regular de 1.75 mm, o que pode ser interessante para posterior aplicação em modelação por deposição de fundido (fused deposition modeling, FDM). Os filamentos apresentavam boa dispersão das nanopartículas, e as EG funcionalizadas apresentavam boa interface com o polímero. As caraterísticas térmicas do polímero não foram alteradas pela presença das nanopartículas, e as propriedades mecânicas foram aumentadas, como se verificou pelos resultados de análise mecânica dinâmica. No entanto a quantidade de EG adicionada não foi suficiente para diminuir a resistividade elétrica do compósito relativamente ao polímero.
Nanotechnology has been finding more applications in several areas. The use of nanocomposites with small quantities of reinforcing nanomaterial has allowed to produce high performance composites with properties that would not be possible to attain with the polymer alone. Nanocomposites’ properties are depended on their preparation technique. The processing step should ensure good nanoparticle dispersion and distribution in the polymeric matrix and to stablish a good polymer/reinforcement interface. Carbon nanotubes, graphene and graphite are some of the nanoparticles that are showing interest for a wide range of applications. In this project the influence of the incorporation of exfoliated graphite in polystyrene composite’s properties was studied. Composites of polystyrene and functionalized exfoliated graphite were prepared with different compositions. These nanocomposites were extruded in filaments form. Then, the characterization of those filaments was carried out to evaluate diameter, morphology, nanoparticle dispersion, electric resistivity, thermal characteristic and mechanical properties. In the present work nanocomposite filaments with regular cylindrical cross-section of 1.75 mm were produced. These filaments may be interesting for applications such as fused deposition modeling. The filaments showed a good dispersion of the nanoparticles and the functionalized nanoparticles established a good interface with the polymer. The thermal characteristics of the polymer were not affected by the presence of EG, and the composite mechanical properties were enhanced, as observed by dynamic mechanical analysis. However, the incorporation of EG was not sufficient to reduce the electrical resistivity of the nanocomposite filaments relative to the polymer.
39
Lee, Chia-Hsin, und 李佳欣. „Novel Applications of the Exfoliated Montmorillonite on Nanocomposites“. Thesis, 2009. http://ndltd.ncl.edu.tw/handle/57057168787827435756.
Der volle Inhalt der QuelleAnnotation:
碩士國立臺灣大學
材料科學與工程學研究所
97
In this thesis, we fabricated the exfoliated montmorillonite (MMT) nanoplatelets by solvent extraction from PMMA/exfoliated MMT nanocomposites, and focused on their novel applications. In the first part, the basic adsorption isotherms of exfoliated MMT was studied by cationic ruthenium dye and methylene blue; it showed less amount of dye molecules adsorbed on exfoliated MMT than pristine MMT reported on literature, so we proposed that it resulted from the remaining PMMA on the nanoplatelets. Moreover, the dye molecules would make the exfoliated MMT nanoplatelets re-stacking back to lamellar structure similar to pristine MMT, which had been revealed by transmitting electron microscopy and X-ray diffraction. The fast adsorption process was observed and the formed separating phase would immediately float on the solution, this made the exfoliated MMT become a promising material for heavy metal removal. Moreover, the cationic poly (ethylene imine) (PEI) was also mixed with exfoliated MMT to form a new biomaterial for gene delivery, the morphology of this nanocomposite was investigated by TEM, and cytoxicity test was carried out by MTT assay; it was inspiring that the toxicity of PEI/ exfoliated MMT nanocomposites were lower than that of the pristine PEI, which might be an optimistic biomaterial suitable for gene delivery. In the second part, we applied the exfoliated MMT nanoplatelets to the electrolyte system of dye-sensitized solar cell (DSSC). As the exfoliated MMT was added into ionic liquid of 1-methyl-3-propylimidazolium iodide (MPII), the whole mixture became gels. The performance of ionic liquid-based electrolyte system incorporating exfoliated MMT was evaluated. The efficiency of resulting DSSC was higher than that with the original ionic liquid; the photoelectrochemical properties were also studied by electrochemical impedance spectroscopy (EIS). Furthermore, in order to increase the efficiency of DSSC, we added carbon nanotubes to the MMT containing ionic liquid-based electrolyte system. The performance of DSSC with this novel electrolyte could reach 7.8% conversion efficiency in average. This well-performed DSSC also showed a very stable long-term stability, which made this device possible to join the competition of commercial solar cell industry.
40
Martins, Helena Patrícia Lima. „Filamentos condutores baseados em compósitos com nanopartículas de carbono“. Master's thesis, 2017. http://hdl.handle.net/1822/49571.
Der volle Inhalt der QuelleAnnotation:
Dissertação de mestrado integrado em Engenharia de PolímerosO objetivo principal do presente trabalho é estudar o efeito das condições pós-extrusão nas propriedades finais de filamentos produzidos a partir de nanocompósitos de matriz termoplástica PEEK reforçada com nanotubos de carbono e grafite exfoliada. Inicialmente, preparou-se o nanocompósito de matriz polimérica PEEK, reforçado com 4% em massa de nanotubos de carbono (CNT) e 3% em massa de grafite exfoliada (GnP), utilizando uma extrusora duplo-fuso co-rotativa. O nanocompósito foi granulado em linha. Numa fase seguinte, foram produzidos filamentos de PEEK e de nanocompósito (PEEK + 4wt% CNT + 3wt% GnP) utilizando uma linha de extrusão de monofilamentos. As condições pósextrusão, razão de estiramento e a temperatura da estufa de estiramento, foram variadas de forma a sujeitar os filamentos a diferentes níveis de estiramento. Os filamentos obtidos foram posteriormente caracterizados em termos de diâmetro, condutividade elétrica, comportamento mecânico à tração e propriedades térmicas. Por fim, sujeitou-se uma amostra de nanocompósito a um ensaio de relaxação térmica de modo a analisar o seu efeito nas propriedades finais. Os resultados permitem concluir que os filamentos apresentaram boas propriedades elétricas, térmicas e mecânicas. No caso dos filamentos nanocompósitos, quando se aumenta a razão de estiramento diminui o diâmetro e a condutividade elétrica, mas mantém-se o comportamento semicondutor, e aumenta o módulo de Young. A gama de temperaturas utilizada na estufa de estiramento não influenciou significativamente as propriedades elétricas, térmicas e mecânicas. O ensaio de relaxação térmica não influenciou as propriedades térmicas e elétricas da amostra do nanocompósito.
The main objective of the present work is to study the effect of post extrusion conditions on the final properties of filaments produced from PEEK thermoplastic matrix nanocomposites reinforced with carbon nanotubes and exfoliated graphite. This work begun with the preparation of the PEEK polymer matrix nanocomposite by reinforce it with 4 wt% of carbon nanotubes (CNT) and 3 wt% of exfoliated graphite through a corotating double-screw extruder. The nanocomposite was granulated in line. In a following step, PEEK and nanocomposite filaments (PEEK + 4wt% CNT + 3wt% GnP) were produced using a monofilament extrusion line. The post extrusion conditions, draw ratio and temperature of the drawing greenhouse were varied to subject the filaments to different drawing levels. The obtained filaments were later characterized in terms of diameter, electrical conductivity, mechanical behavior to traction and thermal properties. Lastly, a sample of nanocomposite was subjected to a thermal relaxation test to analyze the effect on its final properties. The obtained results allow to conclude that the filaments in study have good electrical, thermal and mechanical properties. In the case of the nanocomposite filaments, it was observed that as the draw ratio is increased, the diameter and electrical conductivity decreases, the semiconductor behavior remains, and the Young's modulus increases. The range of temperatures used in the stretching oven didn’t significantly influenced the electrical, thermal and mechanical properties. The thermal relaxation test did not influence the thermal and electrical properties of the nanocomposite sample.
41
WAN, CHI-YANG, und 萬齊洋. „Electromagnetic Wave Absorption Using Morphology-Altered Exfoliated Graphite Nanoplatelets“. Thesis, 2019. http://ndltd.ncl.edu.tw/handle/b69qb6.
Der volle Inhalt der Quelle
42
Ya-HsuanTsai und 蔡雅璿. „Fabrication and Electrical Transport Measurement of Exfoliated BiSbTeSe2 Devices“. Thesis, 2018. http://ndltd.ncl.edu.tw/handle/b3gtx8.
Der volle Inhalt der Quelle
43
Chalasani, Rajesh. „Functionalized Nanostructures : Iron Oxide Nanocrystals and Exfoliated Inorganic Nanosheets“. Thesis, 2013. http://etd.iisc.ernet.in/2005/3463.
Der volle Inhalt der QuelleAnnotation:
This thesis consists of two parts. The first part deals with the magnetic properties of Fe3O4 nanocrystals and their possible application in water remediation. The second part is on the delamination of layered materials and the preparation of new layered hybrids from the delaminated sheets.
In recent years, nanoscale magnetic particles have attracted considerable attention because of their potential applications in industry, medicine and environmental remediation. The most commonly studied magnetic nanoparticles are metals, bimetals and metal oxides. Of these, magnetite, Fe3O4, nanoparticles have been the most intensively investigated as they are, non-toxic, stable and easy to synthesize. Magnetic properties of nanoparticles such as the saturation magnetization, coercivity and blocking temperature are influenced both by size and shape. Below a critical size magnetic particles can become single domain and above a critical temperature (T B , the blocking temperature) thermal fluctuations can induce random flipping of magnetic moments resulting in loss of magnetic order. At temperatures above the blocking temperature the particles are superparamagnetic. Magnetic nanocrystals of similar dimensions but with different shapes show variation in magnetic properties especially in the value of the blocking temperature, because of differences in the surface anisotropy contribution. The properties of magnetic nanoparticles are briefly reviewed in Chapter 1. The objective of the present study was to synthesize Fe3O4 nanocrystals of different morphologies, to understand the difference in magnetic properties associated with shape and to explore the possibility of using Fe3O4 nanocrystals in water remediation.
In the present study, oleate capped magnetite (Fe3O4) nanocrystals of spherical and cubic morphologies of comparable dimensions (∼10nm) have been synthesized by thermal decomposition of FeOOH in high-boiling octadecene solvent (Chapter 2). The nanocrystals were characterized by XRD, TEM and XPS spectroscopy. The nanoparticles of different morphologies exhibit very different blocking temperatures. Cubic nanocrystals have a higher blocking temperature (T B = 190 K) as compared to spheres (T B = 142 K). From the shift in the hysteresis loop it is demonstrated that the higher blocking temperature is a consequence of exchange bias or exchange anisotropy that manifests when a ferromagnetic material is in physical contact with an antiferromagnetic material. In nanoparticles, the presence of an exchange bias field leads to higher blocking temperatures T B because of the magnetic exchange coupling induced at the interface between the ferromagnet and antiferromagnet. It is shown that in these iron oxide nanocrystals the exchange bias field originates from trace amounts of the antiferromagnet wustite, FeO, present along with the ferrimagnetic Fe3O4 phase. It is also shown that the higher FeO content in nanocrystals of cubic morphology is responsible for the larger exchange bias fields that in turn lead to a higher blocking temperature.
Magnetic nanoparticles with moderate magnetization can be easily separated from dispersions by applying low intensity magnetic fields. Oleate capped spherical and cubic iron oxide nanocrystals have considerable magnetic moment and hence have the potential as host-carriers for magnetic separation in environmental remediation. These nanocrystals are, however, dispersible only in non-polar solvents like chloroform, toluene, etc. Environmental remediation requires that the nanocrystals be water dispersible. This was achieved by functionalizing the surface of the iron oxide nanocrystals by coordinating carboxymethyl-β-cyclodextrin (CMCD) cavities (Chapter 3). The hydroxyl groups located at the rim of the anchored cyclodextrin cavity renders the surface of the functionalized nanocrystal hydrophilic. The integrity of the anchored CMCD molecules are preserved on capping and their hydrophobic cavities available for host-guest chemistry. The CMCD capped iron oxide particles are water dispersible and separable in modest magnetic fields (<0.5 T). Small molecules like naphthalene and naphthol can be removed from aqueous media by forming inclusion complexes with the anchored cavities of the CMCD-Fe3O4 nanocrystals followed by separation of the nanocrystals by application of a magnetic field. The adsorption properties of the iron oxide surface towards arsenic ions are unaffected by the CMCD capping so it too can be simultaneously removed in the separation process.
To extend the application of the iron oxide nanocrystals so that they can both capture and destroy organic contaminants present in water, cyclodextrin functionalized water dispersible core-shell Fe3O4@TiO2 (CMCD-Fe3O4@TiO2) nanocrystals have been synthesized (Chapter 4). The application of these particles for the photocatalytic degradation of endocrine disrupting chemicals (EDC), bisphenol A and dibutyl phthalate, in water is demonstrated. EDC molecules that may be present in water are captured by the CMCD-Fe3O4@TiO2 nanoparticles by inclusion within the anchored cavities. Once included they are photocatalytically destroyed by the TiO2 shell on UV light illumination. The magnetism associated with the crystalline Fe3O4 core allows for the magnetic separation of the particles from the aqueous dispersion once photocatalytic degradation is complete. An attractive feature of these ‘capture and destroy’ nanomaterials is that they may be completely removed from the dispersion and reused with little or no loss of catalytic activity.
The second part of the thesis deals with the intercalation of surfactants in inorganic layered solids and their subsequent delamination of the functionalized solid in non-polar solvents. The solids investigated were - the anionic layered double hydroxides (LDH), the 2:1 smectite clay, montmorillonite (MMT), layered metal thiophosphates (CdPS3) and graphite oxide (GO).
Layered Double Hydroxides (LDH) are lamellar solids of the general chemical formula [M0(1−x)Mx(OH)2], where M0 is a divalent metal ion and M a trivalent ion. The structure of the Mg-Al layered double hydroxide (Mg-Al LDH) may be derived from that of brucite, Mg(OH)2, by isomorphous substitution of a part of the Mg2+ by trivalent Al3+ ions with electrical neutrality maintained by interlamellar exchangeable ions like nitrate or carbonate. The ion exchange intercalation of the anionic surfactant dodecyl sulfate (DDS) in an Mg-Al LDH and the subsequent delamination of the surfactant intercalated LDH in non-polar solvent is reviewed in Chapter 5. Delamination results in a clear dispersion of neutral nanosheets. The delaminated sheets are neutral as the surfactant chains remain anchored to the inorganic sheet. On solvent evaporation, the sheets re-stack to give back the original surfactant intercalated solid.
This strategy for delamination of layered solids by intercalation of an appropriate surfactant followed by dispersing in a non-polar solvent has been extended to montmorillonite (MMT) and cadmium thiophosphates (CdPS3) by ion-exchange intercalation of the cationic surfactant dioctadecyldimethylammonium bromide (DODMA) followed by sonication in non-polar solvents e.g. toluene or chloroform as in the case of the LDH (Chapter 6). The nanosheets of the MMT and CdPS3 are electrically neutral as the surfactant chains remain anchored to the inorganic sheet even after exfoliation. Graphite oxide (GO) too can be delaminated by functionalizing the sheets by covalently linking oleylamine chains to the GO sheets via an amide bond. The oleylamine functionalized GO is easily delaminated in non-polar solvents to give electrically neutral GO nanosheets.
It is shown in Chapter 7 that the 1:1 mixtures of dispersions of montmorillonite-DODMA with Mg-Al LDH-DDS nanosheets can self assemble, on solvent evaporation, to give a new layered solid with periodically alternating montmorillonite and LDH layers. In this method attractive forces between the neutral exfoliated nanosheets of cationic and anionic ensures self-assembly of a perfectly periodic alternating layered structure. The method has been extended to synthesize new layered solids in which surfactant tethered cationic and anionic inorganic sheets alternate. The hybrid solids synthesized are CdPS3—MgAl-LDH, CdPS3—CoAl-LDH, GO—MgAl-LDH, GO—CoAl-LDH. The procedure outlined in Chapter 7 allows for a simple, but versatile, method for generating new periodically ordered layered hybrid solids by self-assembly.
44
Hung, Ta-Jen, und 洪達任. „Antimicrobial effects of silver nanoparticles immobilized on exfoliated platelet clay“. Thesis, 2007. http://ndltd.ncl.edu.tw/handle/37626853048408756799.
Der volle Inhalt der QuelleAnnotation:
碩士中興大學
生命科學系所
95
Silver is been known as a bactericidal agent. Silver nanoparticle, as the silver ion, also has bactericidal effect. AgNP/NSP and AgNP/SWN, the materials used in this article, are synthesized by using silicate clays as the dispersing agent to stabilize and immobilize silver nanoparticles. We demonstrate that AgNP/NSP and AgNP/SWN not only have broad-spectrum antibacterial activity, but also can inhibit the growth of fungus spores. Besides, AgNP/NSP and AgNP/SWN also can prevent bacteria infection, as effective as silver sulfadiazine does, in null mice which have burn wound. According to the limited diffusion of disc diffusion assay, we infer that the bactericidal effect of silver nanoparticles on AgNP/NSP and AgNP/SWN is not dependent on the release of silver ion from Ag nanoparticles. We speculate that the antibacterial activity of AgNP/NSP and AgNP/SWN may differ from that of the ionized silver. Observation by using transmission electron microscope (TEM) revealed that AgNP/NSP-treated Staphylococci show intact cell membrane structure, indicating that the influence of AgNP/NSP on bacteria may different with that of silver ion. The result of two-dimensional electrophoresis (2-DE) showed that membrane proteins, ranging among pI=7.0-10.0, are disappeared after treatment of AgNP/NSP. In contrast, the profiles of basic cytosol proteins were not significantly altered after treatment. Taken together, these results demonstrated that AgNP/NSP and AgNP/SWN are effective and safe antibacterial agents without the concerns of generation of resistant strains and metal deposit in the applied body.
45
Moustafa, Ahmed Mohamed Abdel-hakim Cannon Fred S. „Fabrication, characterization and oil spill remediation properties of exfoliated graphite“. 2009. http://etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-4052/index.html.
Der volle Inhalt der Quelle
46
Do, In-Hwan. „Metal decoration of exfoliated graphite nanoplatelets (xGnP) for fuel cell application“. Diss., 2008.
Den vollen Inhalt der Quelle findenAnnotation:
Thesis (Ph. D.)--Michigan State University. Dept. of Chemical Engineering and Materials Science, 2008.Title from PDF t.p. (viewed on July 23, 2009) Includes bibliographical references. Also issued in print.
47
Carvalho, Ana Rita Malheiro da Silva. „Influência do teor de grafite exfoliada nas propriedades do polipropileno isotático“. Master's thesis, 2017. http://hdl.handle.net/10316/83196.
Der volle Inhalt der QuelleAnnotation:
Dissertação de Mestrado Integrado em Engenharia do Ambiente apresentada à Faculdade de Ciências e TecnologiaO principal objetivo deste trabalho é avaliar a viabilidade da incorporação de grafite recuperada de elétrodos em fim de vida provenientes da industria metalomecânica numa matriz de polipropileno, face à adição de grafeno multicamadas comercial. O polipropileno foi escolhido como material base pelo facto de ser um dos polímeros mais comercializados, cujo o seu processamento é fácil e apresenta uma reciclabilidade muito alta. Os nanocompósitos foram produzidos por um processo de fusão e a sua caracterização foi realizada a partir da injeção de provetes. O foco deste trabalho foi a caracterização das propriedades mecânicas com a realização de ensaio de tração e flexão em três pontos. Foram analisados reforços com cargas de 0.5%wt e 1%wt de grafite recuperada e grafeno multicamadas.O principal objetivo deste trabalho é avaliar a viabilidade da incorporação de grafite recuperada de elétrodos em fim de vida provenientes da industria metalomecânica numa matriz de polipropileno, face à adição de grafeno multicamadas comercial. O polipropileno foi escolhido como material base pelo facto de ser um dos polímeros mais comercializados, cujo o seu processamento é fácil e apresenta uma reciclabilidade muito alta. Os nanocompósitos foram produzidos por um processo de fusão e a sua caracterização foi realizada a partir da injeção de provetes. O foco deste trabalho foi a caracterização das propriedades mecânicas com a realização de ensaio de tração e flexão em três pontos. Foram analisados reforços com cargas de 0.5%wt e 1%wt de grafite recuperada e grafeno multicamadas.
The main objective of this work is to evaluate the feasibility of the incorporation of graphite recovered from end - of - life electrodes from the metal - mechanical industry into a polypropylene matrix, in addition to the addition of commercial multilayer graphene.Polypropylene has been chosen as the base material in that it is one of the most commercially available polymers whose processing is easy and has a very high recyclability.The nanocomposites were produced by a fusion process and their characterization was performed from the injection of test pieces. The focus of this work was the characterization of the mechanical properties with the accomplishment of test of traction and flexion in three points. Reinforcements with loads of 0.5% wt and 1% wt of recovered graphite and multilayer graphene were analyzed. The main objective of this work is to evaluate the feasibility of the incorporation of graphite recovered from end - of - life electrodes from the metal - mechanical industry into a polypropylene matrix, in addition to the addition of commercial multilayer graphene.Polypropylene has been chosen as the base material in that it is one of the most commercially available polymers whose processing is easy and has a very high recyclability.The nanocomposites were produced by a fusion process and their characterization was performed from the injection of test pieces. The focus of this work was the characterization of the mechanical properties with the accomplishment of test of traction and flexion in three points. Reinforcements with loads of 0.5% wt and 1% wt of recovered graphite and multilayer graphene were analyzed.
48
Mulange, wa Mulange Delphin. „Stabilization of Cr(VI) from fine ferrochrome dust using exfoliated vermiculite“. Diss., 2011. http://hdl.handle.net/2263/28532.
Der volle Inhalt der QuelleAnnotation:
It was been reported that untreated wastes from ferrochrome plants release heavy metals including lead, chromium, copper, cadmium, zinc and nickel in the environment. Some of these metals such as hexavalent chromium are potentially toxic and carcinogenic, and can cause a serious threat to human health. The contamination of terrestrial and aquatic ecosystems by hexavalent chromium is worldwide of major environmental concern, especially in South Africa which is the largest producer of chromite and ferrochrome. Therefore, the pre-treatment of these wastes before landfill is of great importance to prevent the contamination of the ecosystems. In the present study, vermiculite, a natural occurring mineral, has been tested for its adsorption effectiveness in removing Cr(VI) from ferrochrome dust leachate. Batch adsorption studies have been carried out to determine the effect of pH, contact time and adsorbent dose on the removal of Cr(VI). The process was found to be highly pH dependent. The optimum conditions for the removal were found to be at pH 1.5, contact time 2 hours and adsorbent dose 10 g.L-1. According to kinetic and isotherm studies, the process is best fitted by the pseudo-second order kinetic model, and to both Langmuir and Freundlich isotherms. The maximum adsorption capacity was found to be 23.25 mg.g-1. Thermodynamic parameters show the spontaneous and endothermic nature of Cr(VI) adsorption onto vermiculite.Dissertation (MSc)--University of Pretoria, 2011.
Materials Science and Metallurgical Engineering
unrestricted
49
Tye, Ching Thian. „Studies of exfoliated molybdenum disulfide catalyst in hydrocracking and hydroprocessing reactions“. Thesis, 2006. http://hdl.handle.net/2429/18221.
Der volle Inhalt der QuelleAnnotation:
Studies of MoS₂ catalysts have demonstrated a close relationship between catalyst activity in hydroprocessing and the structure of the MoS₂. Most reports have focused on hydrodesulfurization and hydrogenation and some of these remain somewhat controversial. Moreover, the effect of MoS₂ structure on heavy oil hydrocracking has not been well studied. In this work, exfoliated MoS₂ was used to study the catalyst structure-activity relationship in Cold Lake heavy oil hydrocracking and model compound hydroprocessing. The exfoliated MoS₂ is dispersed directly in the oil eliminating the influence of catalyst support, and the laminar structure of exfoliated MoS₂ provides an interesting framework to study the relationship between catalyst activity and structure. In heavy oil hydrocracking at 415°C, exfoliated MoS₂ had similar liquid and coke yields but exhibited a better quality liquid product, especially in asphaltene and microcarbon residue removal, than MoS₂ derived from molybdenum naphthenate (MoNaph). In addition, the feasibility of recycling coke was confirmed as more than 90% of Mo resided in the coke after reaction and the spent catalyst-in-coke was active in Cold Lake heavy oil hydrocracking. The activity of exfoliated MoS₂ for hydroprocessing at 350°C was also determined using various model reactants. The reactants studied were naphthalene for hydrogenation, dibenzothiophene for hydrodesulfurization, quinoline and carbazole for hydrodenitrogenation, and phenol for hydrodeoxygenation. Again, the resulting catalyst activity was compared to MoNaph derived MoS₂. Exfoliated MoS₂ gave better overall hydrodesulfurization and hydrodeoxygenation as compared to MoNaph derived MoS₂. In contrast, MoNaph derived MoS₂ showed higher hydrogenation and hydrodenitrogenation activities. These results were a consequence of the morphological differences between the two catalysts in the model systems. The activity of exfoliated MoS₂ in hydrodesulfurization of dibenzothiophene was further compared to that of crystalline MoS₂, MoNaph, and ammonium heptamolybdate derived MoS₂. The prepared catalysts had significantly different morphologies, as described by the crystallite stack height and slab length. These data were used to estimate the fraction of rim and edge sites in the crystallites. The catalysts’ selectivity for hydrogenolysis and hydrogenation reactions were shown to correlate with the fraction of rim or edge sites. Selectivity for hydrogenolysis increased as the fraction of edge sites increased.Applied Science, Faculty of
Chemical and Biological Engineering, Department of
Graduate
50
Chen, Yi-An, und 陳怡安. „Studies on synthesis of exfoliate nanosheet and application on orientation control of TiO2-VO2 thin films“. Thesis, 2014. http://ndltd.ncl.edu.tw/handle/zc4f52.
Der volle Inhalt der QuelleAnnotation:
碩士國立臺北科技大學
材料科學與工程研究所
102
The purpose of this thesis is to analyze preparation of exfoliate nanosheet and its applications on orientation control of TiO2 thin films. There are only a few studies on orientation controlled thin films prepared via simple chemical solution deposition. Therefore, there is little application of nanosheet on orientation control of thin film growth with chemical solution deposition. First of all, synthesis of an inorganic layered compound and exfoliate inorganic layered compound via chemical method, such as ion exchange and ion intercalation, can be used to prepare ceramic nanosheet. The crystal structure of layered compound were identified by XRD; KCa2Nb3O10 and HCa2Nb3O10 phase were obtained. TEM showed the exfoliated Ca2Nb3O10 (CNO) nanosheet was sheet-like shaped. SEM and AFM was used to observe the morphology of nanosheet attached on substrate. The nanosheet prepared on the substrate as a template layer. Secondly, TiO2 thin films were deposited on glass substrate by spin coating. The influence of TiO2 thin films with CNO additive was studied. The XRD pattern showed that TiO2 films prepared with CNO nanosheets demonstrated strong (004) peak with increasing annealing temperature, indicating that the c-axis preferential oriented TiO2 thin films were obtained. Experimental results showed that orientation preferred (004) of TiO2 thin films was influenced by CNO concentration and heat treatment temperature. Finally, VO2 thin films were deposited on glass substrates with TiO2 and TiO2-CNO thin films applied as buffer layers between the VO2 films and the substrates in order to investigate the effect of buffer layer on the formation and the thermochromic properties of VO2 film. In this case, electrical and optical properties were analyzed by FTIR, Four-point probe measurement. With TiO2 thin films and TiO2-CNO thin films as buffer layers, the crystallinity increased and reduced the transition temperature and hysteresis width (5°C). The resistance was varied with more than 2 orders under phase transition temperature.